Bridge for stringed musical instruments

ABSTRACT

A bridge for a stringed musical instrument comprises a thin wooden body having a bottom base portion adapted to be supported upon a resonant body member of the instrument and a top crown portion that is formed with grooves for holding individual strings. The base and crown portions have opposed edges that are generally parallel with respect to each other. The crown is formed with baffle slits located adjacent the grooves that are oriented obliquely with respect to the crown edge for redirecting sound waves emitting from strings back to the grooves to produce a ringing tonal effect or to the base to reduce sound attenuation within the bridge.

TECHNICAL FIELD

This invention relates to stringed musical instruments such as banjos,guitars and mandolins, and particularly to bridges used to hold thestrings of such instruments over their resonant bodies and fortransmitting string generated sounds thereto.

BACKGROUND OF THE INVENTION

The strings of many types of musical instruments are held and supportedover their resonant bodies by means of a small, upright member known asa bridge. The bridge, which is usually formed of a thin, hand craftedwooden slab, has a set of grooves along one of its edges in which thestrings are tautly held. In the case of banjos, the bridge is mountedunattachedly upon the resonant diaphragm or head of the banjo and heldin place by the strings.

Heretofore, bridge designs have been focused on attempts to limit soundwave energy absorption and dissipation within the bridge itself and toenhance the tonal clarity of the sounds transmitted by the bridge. Asexemplified by the bridge shown in U.S. Pat. No. 4,667,559, designattempts at achieving this goal have been directed principally atshaping the periphery of the bridge in complex manners on a trial anderror basis. These bridges have been both costly and difficult toreproduce, particularly with consistency.

Accordingly, it is seen that a need remains for a stringed instrumentbridge of relatively simple and reproducible construction and withenhanced sound transmission characteristics. It is to the provision ofsuch that the present invention is primarily directed.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is perspective view of a conventional five-string banjo.

FIG. 2a is a side elevational view of a four-string banjo bridge thatembodies principles of the invention in a preferred form; FIG. 2b is anend elevational view of the bridge.

FIG. 3 is a side elevational view of a five-string banjo bridge thatembodies principles of the invention in another preferred form.

FIG. 4 is a diagrammatical view of sound transmissions in the bridgeshown in FIG. 3.

FIG. 5 is a diagrammatical view of sound transmissions in the bridgeshown in FIG. 2.

FIG. 6 is a front elevational view of a tuning compensation bridge thatembodies principles of the invention.

FIG. 7 is a perspective view of one segment in the tuning compensationbridge shown in FIG. 6.

FIG. 8 is a plan view of the tuning compensation bridge of FIG. 6.

DETAILED DESCRIPTION

Referring now in detail to the drawing, there is shown in FIG. 1 aconventional banjo 10 which has a resonator head or pot 12 from which anelongated neck 14 extends that provides a fretted finger board. Fivewire strings W are mounted to a tailpiece 16 and to a pegged scroll 17so as to extend tautly over the fretted neck. A bridge 20 is detachedlyplaced upon the head diaphragm 19 and supports the strings in aside-by-side spaced array.

With reference to FIG. 3, the bridge 20 is seen in greater detail ashaving a two-piece, thin wooden body 21. The body has a bottom baseportion 21, which typically is made of maple, and a top crown portion22, which typically is made of ebony. The base here has three spacedfeet 24 which have mutually coplanar, flat bottom edges 25 adapted to beset directly upon the diaphragm 19. The crown 22 has a top edge 26 whichis generally flat and oriented substantially parallel with respect tothe feet edges 25.

The crown 22 is conventionally formed with five mutually spaced V-shapedgrooves 27 in which the five banjo strings W are held. Each of thesegrooves is seen to be straddled by a pair of slits 28 and 30 that extenddeeper into the crown than do the grooves 27. The slits of each pairhere are also seen to extend obliquely from the crown edge 26 and toextend from the edge 26 mutually convergently about grooves.

As seen most clearly in FIG. 4, each slit 30 extends from the crown edge26 at an angle a while each slit 28 extends from the crown edge 26 at adifferent angle b. This is to accommodate for the fact that each stringis set in vibration along a plane non-parallel to the banjo head, andthis plane is roughly 7° , positive or negative, as indicated in FIG. 4.Strings are normally picked along different 7° planes by the fingers andthe thumb, as is common with 5-string banjos, requiring the combinationof cuts on the top string to be mirrored. Thus, angles a and b differ byroughly some 14° here. However, this angular difference may varysomewhat because of irregularities in the wood and particularly wherethe crown edges 26 to each side of a groove are not exactly coplanar orwhere the distance between each slit and the groove variessignificantly. For example, an angle a of 79° and an angle b of 65° hasbeen found to produce excellent musical results.

The slit angles a and b are established here so that sound wavesgenerated by a plucked string W, which primarily radiate laterallythrough the bridge, are baffled by the slit and reflected to the crownedge 26. From here they are reflected back to the groove and from thegroove downwardly towards the bridge base and the banjo diaphragm. Inthis manner sound sustention is obtained as well as a ringing effectproduced. The sustenance is believed to be achieved by the fact thatsome waves recirculate many times in the groove-slit-edge-groove circuitbefore being promulgated to the bridge base and diaphragm. A ringingtonal effect is believed to be derived from the frequency phase shiftscreated.

In actuality, of course, sound waves propagate in many directionsthrough the bridge when a string is vibrating. Thus the heavy lines witharrows in FIG. 4 denote that particular path of wave travel that occursfrom the point of wire contact with the groove to in the precisedirection of normal string movements. It should be understood, ofcourse, that all angles of reflections here are equal but opposite tothe angles of wave incidences, and that the change in medium from woodto air at the slits' edge and groove creates the reflections. Since theslits are located so closely to the grooves, lateral emanating soundwaves are quickly directed downwardly to the bridge base and to thediaphragm with minimal attenuation. The result is added volume, clarityand a ringing tonal quality.

With reference next to FIGS. 2 and 5, a four-string banjo bridge 40 isshown which has a crown 41 and a base 42 that has two base feet 43. Thecrown has a top edge 44 which is formed with four wire string holdinggrooves 45. A plurality of slits is again formed in the crown such thata pair of slits 47 and 48 straddles each groove. Each of the slits 48here is essentially the same as the slits 30 in the previously describedembodiment and serves the same function. Each of the slits 47 however isseen to extend obliquely from the crown edge 44 at an angle to redirectsound waves travelling generally laterally from a wire W held within agroove 45 downwardly towards the base portion of the bridge. This servesto amplify the sound in the sense that the sound ultimately generated bythe banjo is louder than that generated with bridges made without thisslit. This is believed to be attributable to the fact that the sound isdirected to the bridge base and banjo diaphragm rather than to the sideedges of the bridge where it is reflected back and forth through thebridge many times. Such back and forth propagations of sound wavesresults in energy dissipation and sound attenuation. It should beappreciated that, if desired, a single slit 47 may be formed between twoadjacent string holding grooves to provide amplification from one of thegrooves and sustenance from the other. The different angles for theslits that straddle the furthest right groove in FIG. 3 is toaccommodate for the fact that the wire held in that groove is plucked bythe thumb at a different angle of attack.

Finally, FIGS. 6-8 show principles of the invention as applied to aconventional tuning compensation bridge 50 that has five segments 51coupled together by a safety string 52. Here it is seen that a pair ofslits 54 straddle a wire receiving groove 55 frame formed in the crownwith the slits extending convergently from the crown. As is well knownby segmenting the bridge its location may be individually adjusted andset for each wire string for tuning compensation. Thus, in thisapplication the term "bridge" is intended to include segmented typebridges as well as unitary bridges.

It thus is seen that a bridge is now provided for stringed musicalinstruments that enhances musical characteristics of the instruments.Though the bridge has been found to be uniquely well suited for use withbanjos, it may be also used on other types of string instruments such asmandolins. In that case the base of the bridge is permanently mounted tothe resonant chamber of the mandolin. Though two preferred embodimentshave been illustrated and discussed in detail, many modifications,additions and deletions may be made thereto without departure from thespirit and scope of the invention as set forth in the following claims.

I claim:
 1. A bridge for a strummed stringed musical instrumentcomprising a thin body having a bottom base portion adapted to besupported upon a resonant member of the instrument and a top crownportion that is formed with a plurality of V-shaped grooves for holdingindividual string members of the instrument, and a plurality of pairs ofsubstantially straight baffle slits that extend convergently from saidcrown edge with each of said pairs of slits straddling a different oneof said grooves and with each slit terminating to the same side of anadjacent groove from which it extends from said crown edge, and whereinsaid base and crown portions have opposed edges that are generallyparallel with respect to each other, whereby some sound waves emittedfrom strings held within said grooves and propagated generally laterallythrough said crown portion are reflected by said baffle slits towardsportions of said crown edge located closely adjacent said straddledV-shaped grooves, back onto said V-shaped grooves for enhanced soundsustention and from said grooves towards said bridge base.
 2. A bridgefor a strummed stringed musical instrument comprising a thin body havinga bottom base portion adapted to be supported upon a resonant member ofthe instrument and a top crown portion that is formed with a pluralityof V-shaped grooves for holding individual string members of theinstrument, and a plurality of pairs of substantially straight baffleslits that extend divergently from said crown edge with each of saidpairs of slits straddling a different one of said grooves, and whereinsaid base and crown portions have opposed edges that are generallyparallel with respect to each other, whereby sound waves emanating fromthe string held with the groove straddled by a pair of baffle slits arereflected by at least one of said slits directly towards said bottombase portion for sound amplification.
 3. The musical instrument bridgeof claim 1 or 2 wherein the baffle slits of each of said pairs of slitsextend from said crown edge at mutually different angles to accommodatefor divergent downstroke and upstroke angles of attack made by strummedstrings.